Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C13/00—Cyclic hydrocarbons containing rings other than, or in addition to, six-membered aromatic rings
  • C07C13/28—Polycyclic hydrocarbons or acyclic hydrocarbon derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
  • C07C2/86—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon
  • C07C2/862—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms
  • C07C2/864—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms the non-hydrocarbon is an alcohol
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
  • C07C5/02—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation
  • C07C5/10—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation of aromatic six-membered rings
  • C07C5/11—Partial hydrogenation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2521/00—Catalysts comprising the elements, oxides or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium or hafnium
  • C07C2521/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
  • C07C2521/08—Silica
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2601/00—Systems containing only non-condensed rings
  • C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
  • C07C2601/14—The ring being saturated

Definitions

• the invention relates to mixtures of cyclohexylbiphenyls, dicyclohexylbenzenes, phenylbicyclohexyls, tercyclohexyls and optionally higher polycyclic hydrocarbons, which mixtures are liquid at room temperature, processes for their preparation and their use as heat transfer media.
• Heat transfer media in the sense of the invention are heat transfer agents which are used, for example, in cooling and heating circuits and in heat recovery units. Such heat transfer media are expected to have, inter alia, a high heat capacity, a high thermal loading capacity and, above all, as low as possible a viscosity, because the viscosity is one of the factors determining the required pump capacity (and thus the suitability of the heat transfer medium for use at low and high temperatures) and the flow rate (and thus the achievable heat transfer and the sizing of the heat exchange surfaces). When the heat transfer media are used for cooling purposes, the lowest possible use temperature is determined by the viscosity.
• chlorinated polyphenyls were the most popular heat transfer media in the past. Since chlorinated polyphenyls have, for the known reasons, no longer been used for this purpose, there has been a switch to non-halogenated polyphenyls and their derivatives, such as, for example, partially hydrogenated terphenyls (Monsanto Company publication, Warmetragermannmaschineen (heat transfer fluids), introductory edition 1991, page 4).
• Terphenyls are obtained as by-products in the preparation of biphenyl. Since the thermal biphenyl synthesis - the pyrogenic benzene dehydrogenation at 700° to 800° C. - is carried out in the presence of carbon disulphide in order substantially to prevent degradation products (carbon black!), the resulting diphenyl and the terphenyls obtained as by-products contain small amounts of sulphur compounds, which, as is known, act as catalyst poisons and therefore make the terphenyl hydrogenation more difficult. An industrially advanced preparation process should take this problem into account.
• the invention therefore relates to mixtures of
• the above mixtures according to the invention can be prepared by hydrogenation of mixtures of cyclohexylbiphenyls and terphenyls.
• cyclohexylbiphenyls have been prepared by reacting biphenyl with cyclohexene or halogenocyclohexane in the presence of typical Friedel-Crafts catalysts, such as, for example, aluminium chloride (Japanese Patent 1973/92 347 of 30.11.1973; Japanese Patent 1974/5949 of 19.1.1974; Japanese Patent 1974/11 860 of 1.2.1974).
• typical Friedel-Crafts catalysts such as, for example, aluminium chloride
• aluminium chloride Japanese Patent 1974/5949 of 19.1.1974
• a further subject of the invention is, therefore, a process for the preparation of cyclohexylbiphenyls from biphenyl and cyclohexanol in the presence of 0.3 to 5 and preferably 0.8 to 2% by weight of bleaching earth, based on biphenyl employed.
• the molar ratio of the starting materials biphenyl and cyclohexanol can vary within wide limits; it is generally 1 to 5 and preferably 2 to 3.
• the reaction temperature is generally 140° to 220° C., preferably 160° to 190° C.
• “Bleaching earths” are understood to be finely divided materials which essentially are derived from aluminium oxides and/or silicon oxides - preferably those having a strip or plate structure.
• Preferred bleaching earths comprise predominantly aluminosilicates such as the montmorillonite group, which includes bentonites, nontronites, baydellites and hectorites, but also kaolins, as well as essentially quartz-like products, such as kieselguhr and related deposits.
• Bleaching earths of this type can be used without pretreatment; preferably, however, they are subjected to a treatment with acid, in particular with an inorganic acid such as sulphuric acid, phosphoric acid, hydrochloric acid, perchloric acid or hydrofluoric acid.
• an inorganic acid such as sulphuric acid, phosphoric acid, hydrochloric acid, perchloric acid or hydrofluoric acid.
• Activated bleaching earths of this type are described, for example, in Ullmanns Encyclopadie der ischen Chemie (Ullmann's Encyclopaedia of Industrial Chemistry), 3rd edition, volume 4, page 541 et seq. (1953), volume 8, pages 801 to 804 (1957) and volume 9, page 271 et seq. (1957), Urban & Schwarzenberg, Kunststoff-Berlin.
• the procedure can, for example, be carried out in such a way that biphenyl and bleaching earth are initially introduced and cyclohexanol is supplied at elevated temperature.
• the resulting water of reaction can be distilled off continuously with the cyclohexene, which is initially formed, and separated off using a water separator.
• the recycled cyclohexene then serves for alkylation of the biphenyl.
• the reaction mixture can be filtered hot, with suction, to remove the catalyst. Excess biphenyl will then be distilled off.
• the distillation residue which essentially consists of cyclohexylbiphenyls, can be processed without further purification steps or purified by distillation.
• cyclohexylbiphenyl in the sense of the invention signifies the reaction product from the cyclohexylbiphenyl preparation including the higher polycyclic hydrocarbons formed as by-products.
• the terphenyl problem described further above can also be satisfactorily resolved using bleaching earth: if bleaching earth is allowed to act on the mixture of terphenyls and cyclohexylbiphenyls intended for hydrogenation and is then separated off, products are obtained which (compared with untreated mixtures) can be hydrogenated considerably more rapidly. Because of the high melting point of the mixture, the separation of bleaching earth from batches on an industrial scale presents difficulties. The reaction proceeds considerably more simply if the mixture is diluted with additional biphenyl. A mixture of this type can be prepared in connection with the synthesis of cyclohexylbiphenyls:
• a further subject of the invention is, therefore, a process for the preparation of the instant heat transfer fluids by partial hydrogenation of a mixture of terphenyls and cyclohexylbiphenyls, characterised in that the mixture used for the hydrogenation, or its components, is/are treated with bleaching earth.
• the mixtures of terphenyls and cyclohexylbiphenyls intended for hydrogenation can also contain these higher polycyclic hydrocarbons; the hydrogenation products can also contain these higher polycyclic hydrocarbons or their hydrogenation products.
• the hydrogenation is as a rule carried out under moderately elevated pressure and at elevated temperature in the presence of 1 to 10, preferably 3 to 6%, by weight of a hydrogenation catalyst, for example a nickel catalyst.
• a hydrogenation catalyst for example a nickel catalyst.
• finely divided metallic nickel on a support or in the form of Raney nickel is used.
• the hydrogenation can be discontinued when the proportion D of the mixtures according to the claim is in the range of 45 to 65% by weight, based on the sum of the components A to D.
• aromatic compounds can be hydrogenated only under forced conditions.
• pressures of at least 100 bar and temperatures of above 250° C. are generally employed (J. Org. Chem., Vol. 30 (1965), p. 384-388; Ullmanns Encyclopadie der ischen Chemie (Ullmann's Encyclopaedia of Industrial Chemistry), 4th edition, volume 9, page 683, Urban & Schwarzenberg, Kunststoff-Berlin 1975). It was therefore completely surprising that the hydrogenation of a mixture of terphenyls and cyclohexylbiphenyls can take place under relatively mild conditions. Instead of expensive high-pressure autoclaves it is thus now possible to use normal reactors.
• a further subject of the invention is, therefore, a process for the preparation of mixtures according to claim 1 by partial hydrogenation of a mixture of terphenyls and cyclohexylbiphenyls in the presence of a hydrogenation catalyst, characterised in that the hydrogenation is carried out at temperatures of 120° to 190° C., preferably of 160° to 180° C., and under pressures of 2 to 25, preferably 8 to 15, bar.
• a further aim of the invention was the provision of an overall concept for the preparation of a modern heat transfer medium using biphenyl and terphenyl as starting materials on as economical a basis as possible.
• the implementation of the processes described represents such a concept using biphenyl and terphenyl as starting materials, which concept leads to the instant heat transfer fluids.
• a further subject of the invention is, therefore, a process for the preparation of instant heat transfer fluids, according to which process biphenyl and cyclohexanol are heated in a molar ratio of (1 to 5):1 in the presence of 0.3 to 5% by weight, based on biphenyl employed, of bleaching earth to a temperature of 140° to 220° C.
• terphenyl in 0.5 to 1.2 times the amount of cyclohexylbiphenyls present in the reaction mixture
• biphenyl in an amount such that the proportion of biphenyl in the crude mixture (after the addition of terphenyl) is at least 30% by weight, are added to the resulting reaction mixture and the resulting mixture is stirred at a temperature of 130° to 160° C.
• the bleaching earth and biphenyl are separated off, the residue is hydrogenated in the presence of a hydrogenation catalyst at a temperature of 120° to 190° C. and under a pressure of 2 to 25 bar until the proportion D in the mixtures according to the claim is in the range of 45 to 65% by weight, based on the components A to D, the hydrogenation catalyst is separated off and the residual reaction mixture is distilled.
• the mixtures according to the invention have a kinematic viscosity of 80 to 90 mm 2 /sec at 20° C. Because of the high boiling points of the individual components, the mixtures according to the invention are outstandingly suitable as heat transfer media in systems under normal pressure.
• a further subject of the invention is the use of the mixtures according to the invention as heat transfer media.
• the resulting distillate is of low viscosity, clear and soluble in toluene; it has a kinematic viscosity of 89 mm 2 /sec at 20° C. It contains:

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• 1991
  • 1991-12-13 DE DE4141191A patent/DE4141191A1/de not_active Withdrawn
• 1992
  • 1992-11-30 EP EP92120436A patent/EP0546419B1/de not_active Expired - Lifetime
  • 1992-11-30 DE DE59205481T patent/DE59205481D1/de not_active Expired - Fee Related
  • 1992-11-30 AT AT92120436T patent/ATE134603T1/de not_active IP Right Cessation
  • 1992-11-30 ES ES92120436T patent/ES2083659T3/es not_active Expired - Lifetime
  • 1992-12-08 JP JP4351374A patent/JPH05271111A/ja active Pending
• 1993
  • 1993-08-20 US US08/110,343 patent/US5384059A/en not_active Expired - Fee Related

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